Catalytic oxidation of ethyl acetate over CuO/ZSM-5 catalysts: Effect of preparation method

A series of CuO/ZSM-5 catalysts with different copper loadings were prepared by impregnation (IM) and chemical vapor deposition (CVD) methods, respectively. Their physicochemical properties were investigated by N2 adsorption/desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectronic spectra (XPS), temperature-programmed reduction by hydrogen (H2-TPR) and temperature-programmed desorption of NH3 (NH3-TPD). The XRD and TEM results demonstrated that the crystallite size of the CuO prepared by CVD method was smaller than that by IM, and the XPS results illustrated that the copper specie was mostly in Cu2+ state and Cu+ co-existed. The performance of catalytic oxidation of ethyl acetate was conducted in the fixed-bed reactor based on CuO/ZSM-5 catalysts. The experimental results showed that the preparation method affected the catalytic activity of CuO/ZSM-5; the CVD catalysts exhibited a higher catalytic activity for ethyl acetate oxidation compared with the IM catalysts at the same copper loadings. Ethanol and acetaldehyde are observed to be the intermediate products in the combustion of ethyl acetate over the synthesized catalysts. The relative amounts of acetaldehyde and ethanol are determined by the selectivity of the catalyst toward acetaldehyde production from ethanol. Particularly, the 3 wt% CVD catalyst showed the best catalytic activity for ethyl acetate oxidation with 90% conversion of ethyl acetate at 235 °C, which was much lower than that of the 3 wt% IM catalyst (278 °C), meanwhile, the intermediate products of the 3 wt% CVD for ethyl acetate oxidation were completely oxidized into CO2 and H2O at temperature as low as 288 °C.